University of Illinois Professor Paul Goldbart is unequivocal when he talks about the theory of superconductivity, advanced 50 years ago by John Bardeen, the UI's two-time Nobel Prize winner, and UI colleagues Leon Cooper and Robert Schrieffer.
Not just a milestone in condensed-matter physics or physics in general, something most physicists would agree upon, but "one of the high-water marks of human thought" is how Goldbart characterized the so-called BCS Theory recently.
"I really feel that," he said.
"This is a theory that had an enormous impact on physics in all areas, I would say," added Goldbart's colleague in the UI Physics Department, Professor Gordon Baym.
So maybe it's no surprise that its golden anniversary is being marked by many scientific conferences, perhaps none a hotter ticket than the four-day event taking place at the UI this week. Eight Nobel laureates are on the schedule of speakers. When the invitations went out, just about everyone said yes.
"People are honored to be associated with this conference," said UI physics Professor Philip Phillips, who chaired the organizing committee.
Perhaps that's because the event takes place at the institution where the theory was spun by Bardeen, his postdoctoral researcher at the time Cooper and then-graduate student Schrieffer, whose doctoral thesis centered on it. The three shared the 1972 Nobel in physics, although the paper outlining their take on superconductivity was published in 1957.
Both Cooper and Schrieffer are to speak at the conference. Bardeen died in 1991.
In a ceremony Thursday, the American Physical Society will designate the old Physics Building, 1304 W. Green St., U, where the three worked, as a site of historic significance with a bronze plaque presented to UI Chancellor Richard Herman.
The UI also will launch a new Institute for Condensed Matter Theory, the branch of physics under which superconductivity falls, with Goldbart as its first director and 2003 physics Nobel winner UI Professor Anthony Leggett as its chief scientist.
UI Professor Dale Van Harlingen, who heads the Physics Department, said the new institute will leverage the UI's stellar reputation and long history in the field. He said it should focus world attention on a program whose mixing of top theoreticians and experimentalists already is widely known as the "Urbana style" of doing physics, a style Bardeen helped institutionalize here.
Leggett won his Nobel for work on superfluidity, a state in which liquid, like current in superconductivity, flows without resistance. His work was essentially an extension of the BCS Theory, he noted.
"I think it really is one of the landmarks in 20th Century physics," Leggett said of the first paper on the theory published by the three UI researchers 50 years ago. "It had a tremendous spinoff on various other areas."
Bardeen won his first Nobel in 1956 for the development of the transistor, the linchpin of the electronic age, at Bell Labs. But he had been working on the superconductivity puzzle even before he arrived at the UI in 1951 and assembled a team here, including Cooper and Schrieffer, with the aim of solving it at last.
"Bardeen had superconductivity on his brain from when he was a graduate student still, that puzzle," said UI Professor Nick Holonyak, Bardeen's longtime friend and first graduate student who went on to develop the light-emitting diode.
Scientists had known about superconductivity at least since 1911, when a Dutch researcher found that super-cooled mercury lost its resistance to the flow of electricity. But no one had adequately explained the physics of how that happened.
Plenty of people had thrown up their hands, so to speak, in the face of the problem, Baym said. But Bardeen refused.
"Bardeen was very stubborn in an absolutely positive way," Baym said.
The three figured out that electrons in the case of superconductivity weren't crystallizing at the low temperature, as in water to ice, but organizing and condensing into, in Goldbart's words, "a rather remarkable state of matter" permitting the free flow of electricity.
Leggett said the achievement was both qualitative and quantitative – they came up with the idea that electrons paired and worked together to make a path for superconductivity, and also with a mathematical formula describing how.
"People had sort of vaguely speculated something like this might go on," Leggett said. "But they hadn't showed why."
Van Harlingen said the theory also is impressive for what has happened to it in the 50 years since: not much.
"It's not only a theory that works, it's sort of the simplest theory that works," he said, noting that attempts to add or subtract from it have generally gone for naught. "They really had it pretty much all right."
Van Harlingen and others said the theory also provided a model that has been extensible to a vast array of problems in physics and other sciences, whether looking at the behavior of subatomic particles or at neutron stars.
In a practical sense, if it has been less influential than Bardeen's other Nobel-winning research effort, the transistor, it nonetheless drives technology ranging from Magnetic Resonance Imaging, or MRI, to radio telescopes and superconducting quantum interference devices, or SQUIDs, used in highly sensitive geologic measurements, among other things.
Meanwhile, scientists have discovered materials with superconductive properties at higher temperatures, a phenomenon they're still working to explain.
Van Harlingen said high-temperature superconductivity, an area in which he's an internationally known expert, holds out particular promise in power transmission. By permitting electricity to be moved over longer distances with minimal loss, it could potentially generate a huge energy savings over today's rather lossy system.